TRASH CAN FURNACE
basic components for this furnace is a common 15 gal galvanized
trash can, a cardboard form, and some pieces of wood for supports.
A suitable piece of pipe for what ever burner you use will also
be needed. In this furnace, I used a piece of 2" iron pipe,
which allow a burner of up to 1 1/2" in diameter to be used..
All items are readily available in home builder or hardware stores.
Trash can with inner chamber
form in place. The inner form is just a cardboard tube, such as
is found in home builder supply stores that is used for forming
concrete. My form was a 9" tube, but I slit it and reduced
it to 7 1/2" in diameter. The form needs to be held securely
in place so it will not move when you cast the refractory. The basic procedure for
casting the refractory is to mix the material as per instructions,
which will make a material with the consistency of a stiff cookie
mix. Place a layer of the material in the form, and tamp with
a wooden 2 x 2. Tamping packs and ensures that you do not get
any voids, which would diminish your insulating ability. Place
more material in form, and tamp again. Repeat until the form is
completely full. Remember, follow the mixing directions for your
material. Usually less water is better.
You will notice
that there is a steel pipe entering the can from the bottom left.
This is just an ordinary piece of 2" steel pipe, which enters
through the side of the can and into the inner chamber. It is
in this tube that you place your burner. The three bolts seen
towards the left end of the tube is used to fasten and adjust
your burner assembly in the tube. This tube just happens to be
10" O.A.L.. The tube is angled towards the chamber wall,
but is horizontal to the ground. This enables the flame from the
burner to sort of swirl around the crucible. The flame goes around
the wall and the side of the crucible then out the vent in the
lid. This also saves a lot of wear and tear on your crucible,
by not having it directly in the path of the flame. You also want
to position this burner mounting tube so it will allow the burner
flame to enter the chamber a contact the lower 1/3 of the crucible.
The lid pictured
above is merely a band of 14 ga. 4" flat iron. Regular galvanized
sheet metal of 26 ga. can be used to fabricate this lid. The center
form is nothing more than a piece of cardboard tube from a roll
of carpet, 4" in diameter. When cast with refractory, this
lid will weigh in the neighborhood of 60 pounds, so handles are
a must. I attached small "L" shaped brackets around
the inside circumference of the lid with a spot welder. Rivets,
bolts etc will also do, or you can just drill holes and thread
the wire used to re-inforce the refractory in place. I placed
my re-enforcing mesh 2 1/2" from the bottom of the band.
Of course the center form is centered. Its important to cast the
lid on a good and flat surface as it must fit pretty close to
the top of the trash can when in use. I placed a piece of plastic
on the concrete floor. I just happened to get a bunch of 5' x
5' x 3/16" thick sheets from the local Sports Authority store
when they changed out their in store displays.
Another view of
both lid and furnace forms.
View of the furnace
after the refractory was cast and tamped. The top needs to be
fairly smooth to make a good seal with the lid. Refractory actually
entrains air pockets in its process of curing, which further adds
to its insulating ability. I used a hot melt glue gun to seal
up the opening that I made for the burner mount tube, so it did
not leak while the refractory was curing.
Both the furnace
body and lid has been cast, so now its just a matter of time for
it to harden, so its the perfect time to build the burner and
accessories that will be needed.
The burner I used
is called the Monster Burner. It is made entirely of common plumbing
Wenig, designed this particular burner and I must say, it
is simple and works like a champ. I designed and built the air
choke assembly and simply screwed it to the back of the reducing
bell. An air choke is necessary to make more precise adjustments
of your air to fuel mix to get the most out of your burner. This
burner is quiet, and very efficient. To see a schematic of this
burner click here.
I won't get into
the details here on building the burner, but if your interested,
you can find a drawing of this burner and many others at Ron Reils web site. His site
has a wealth of information on forges and foundries. Take me to
You will also
need to read all the associated links under the Monster Burner
to get the fuel jetting size etc. The Foundry Melt Logs
are especially interesting and impressive.
Here is a side
view of the burner on its initial run.
The device on
the end of the burner tube is called a flare. It is necessary
to install a flare on the burner if it is run outside of a furnace.
Due to the design of this burner, air is induced at the rear and
increased in velocity as it is mixed with propane gas as it travels
down the tube. It is traveling at such speed that it will blow
itself out as it leaves the end of the tube. A flare reduces the
fuel/air mix down to a speed that enables it to burn at the end
of the tube instead of being blown out. Once tuned properly the
flare is removed and the burner is inserted into the furnace burner
mounting tube. For more information on burner flares and how to
make them visit the Lionel
Oliver at his Lab.
Lionel has a lot of unique and interesting information on
metal casting and numerous other projects on his website.
Take me to the
main index page. click